1. Field of the Invention
The invention relates to alighting device, a method for controlling the lighting device and a circuit thereof, more particularly to an adjustable lighting device, a method for setting and adjusting light emitted therefrom, and a light-adjusting circuit thereof.
2. Description of the Related Art
FIG. 1 illustrates a conventional adjustable lighting device 1 including a light emitting diode (LED) module 10 and a light-adjusting circuit 11. The adjustable lighting device 1 can be electrically connected to an alternating current (AC) power source for receiving an AC power therefrom, and is operable to selectively emit light with various illumination states, each of which corresponds to a specific brightness and a specific color temperature.
The LED module 10 is operable to emit the light with various illumination states, and includes a first light emitting unit 101 that is operable to emit light with a warm color, and a second light emitting unit 102 that is operable to emit light with a cold color. Each of the light emitting units 101 and 102 has a plurality of LEDs. The illumination state of the light emitted from each of the first and second light emitting units 101 and 102 is positively related to an adjustable electric current flowing therethrough. Thus, various illumination states of the light emitted by the LED module 10 can be obtained by adjusting the electric current flowing through each of the first and second light emitting units 101 and 102.
The light-adjusting circuit 11 includes a power switch 110, an AC/DC converter 111, a control unit 112 and an adjusting unit 114.
The power switch 110 is electrically connected to the AC power source for receiving the AC power, and is switchable between a closed state, in which the power switch 110 is configured to transmit the AC power, and an open state, in which the powers witch 110 is configured to interrupt transmission of the AC power.
The AC/DC converter 111 is electrically connected to the power switch 110, and is operable to convert the AC power received from the power switch 110 into a direct current (DC) power and to output the DC power when the power switch 110 is in the closed state.
The control unit 112 is electrically connected to the AC/DC converter 111, and includes a counter 113 and a capacitor (C). The capacitor (C) is charged to store electrical energy when the power switch 110 is in the closed state, and can provide the counter 113 with electric power when the power switch 110 is in the open state. Accordingly, the counter 113 is operable to count a number of times that the power switch 110 is switched from the open state to the closed state, and the counted number of times corresponds to a particular one of the illumination states. The control unit 112 is operable to output a current setting value, which is associated with the particular one of the illumination states, according to the counted number of times.
The adjusting unit 114 is electrically connected to the AC/DC converter 111, the control unit 112, the first light emitting unit 101 and the second light emitting unit 102. When the power switch 110 is in the closed state, the adjusting unit 114 is operable to adjust the electric current to the first light emitting unit 101 and the second light emitting unit 102 according to the current setting value received from the control unit 112. Thus, a user can adjust the illumination state of the light emitted by the adjustable lighting device 1 by switching the power switch 110 from the closed state to the open state and then switching back to the closed state within a threshold time, which is related to a discharge time of the capacitor (C).
Nonetheless, the conventional adjustable lighting device 1 has several drawbacks. For example, when the power switch 110 is first switched from the open state to the closed state, the adjustable lighting device 1 emits the light with a default illumination state. When the user desires another illumination state, the user has to switch the power switch 110 multiple times. This results in waste of time and excessive usage of the power switch 110, such that the service life of the power switch 110 may be short. In addition, there is a requirement of the capacitor (C) providing the electric power to the counter 113 to keep track of the counted number of times when the power switch 110 is in the open state. As a result, a manufacturing cost of the conventional adjustable lighting device 1 is increased.